Best magnum MPG?

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75slant6

75slant6

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Ok guys, I'm in the middle of putting a 5.9 magnum with a 600 cfm eddy carb in my 72 Duster. Today I filled up my 01 Ram 1500 with a 5.9 and got a whopping 10.7 mpg. Now I know the truck is much heavier, is 4x4 and has more wind resistance but it got me thinking, how much are y'all getting for mpg? If possible, include what car, trans, tire size and gear ratio y'all have and carb or efi. Fire away.
 
Geez..........Years ago a good friend had a (then new) about a 74 Dodge 1/2 T 360 2bbl that thing would bump up against 14. It was a short box 4x4, 4 speed.
 
I know it's not a Magnum, but the LA 360 in the 71 Dart I had years ago did 20 on the highway with 3.23 gears. It had a Thermoquad.
 
RustyRatRod said:
I know it's not a Magnum, but the LA 360 in the 71 Dart I had years ago did 20 on the highway with 3.23 gears. It had a Thermoquad.
Click to expand...

So in my 72 Duster with a 3.23 rearend, 1406 edlebrock and an overdrive 5 speed I should easily hit 20+? I'm hoping for 25+ on the highway but 20+ would be great too!
 
I don't see why it couldn't.
 
I just checked my '01 Ram 3/4 ton 2wd. 5.9 auto with 229,*** miles. Got 17.4 mpg going back and forth to work. Went 429 miles and refilled at the exact same pump.

5.2 Durango averaged between 18-20 mpg on a 2000 mile trip last year rolling 70 mph.
 
318willrun said:
I just checked my '01 Ram 3/4 ton 2wd. 5.9 auto with 229,*** miles. Got 17.4 mpg going back and forth to work. Went 429 miles and refilled at the exact same pump.

5.2 Durango averaged between 18-20 mpg on a 2000 mile trip last year rolling 70 mph.
Click to expand...

I don't even like you.... Lol. I think something's off with my truck, trans needs work for one but I think it also needs a tune up
 
Dad had a 76 Charger with a 360 2 bbl and that got 20 mpg highway. With a 25 gallon tank it could go 500 miles between gas stops...

You had to stop to pee before you could run out of gas on a long road trip....

Our 98 Grand Cherokee 5.9 drinks gas like a drunken sailor...
 
Sure like to hear she numbers for cars that have had a Magnum swapped in. Trucks and such are nice, but more an apples to oranges comparisons.
 
My 318 truck used to get around that in city driving in 4wd or just under 10 pulling a trailer, 14 hwy. 4.7 would get 13ish around town beat on, around 20 on the road. My 318 F car would get like 25 on the road, with the 360 it'd get close to 23.
 
75slan6,
I doubt you will ever get more than mid teens with an edelbrock carb...while they are good daily drivers, they are not known for good mpg.

I built a 70 Swinger for my son over 10 years ago when he was learning to drive, 1998 Dakota 5.2 Magnum with 42RE out of 3.9 Dakota. Swinger was 318, 904, 8 3/4 3.23 SG Power Disk, P steering, factory AC. I installed with headers, 14" K&N, 850 CFM TB, 1.7 Rockers, built FI pump in tank, used Dakota PS pump, and AC pump. Est 300HP at crank. 24-25 mpg at 80 on freeway with the AC spittin out ice cubes.

We also build Magnum powered Wranglers and I have had several TJ Wranglers with 5.2 5 speed swaps and 4.10 gears that got 20-22 on freeway. not bad for 4000 lb barn door.

If you want power and mpg, its all about injection and overdrive....you have a 5 speed so take the FI plunge, you wont be sorry you did. Many affordable options now, from factory OBD I or II system to something as simple as a FITech TB unit.
 
http://www.hughesengines.com/Index/...cyAmIFBsZW51bSBSZXBhaXIgS2l0cw==&partid=27091
fix intake mpg goes back up lol on efi.

my 68 valiant, sedan, 360 magnum, 2.47 close ratio 4 speed, 8 3/4 w power lok, 2.94 rear gear, gets 17mpg when I keep my foot out of it. 3310 750 holley vac secondary, hei module conversion, crosswind intake, stock motor, no cam, no valve springs. 14 inch rallye wheels. car would probably get 20+ with 15 tires and smaller carb
 
acpat said:
http://www.hughesengines.com/Index/...cyAmIFBsZW51bSBSZXBhaXIgS2l0cw==&partid=27091
fix intake mpg goes back up lol on efi.

my 68 valiant, sedan, 360 magnum, 2.47 close ratio 4 speed, 8 3/4 w power lok, 2.94 rear gear, gets 17mpg when I keep my foot out of it. 3310 750 holley vac secondary, hei module conversion, crosswind intake, stock motor, no cam, no valve springs. 14 inch rallye wheels. car would probably get 20+ with 15 tires and smaller carb
Click to expand...

Might even see more with a better cam. 5.9 factory cam is well know for being a gas sucking turd stick. You can have a mpg friendly cam ground that will make more power and lots of torque. With those gears you would probably break into 20 mpg with factory injection.
 
I know this is 'apples and oranges' but, just for comparison, my '09 Ram 1500 with a 5.7 Hemi has shown a best of 25mpg freeway cruising at 65mph.
Fairly heavy, aerodynamic-deficient truck rated at 390hp. Can't ask for much better than that.
 
Lelo Dart said:
5.9 99 Dak- 16 MPG driving like grandma.
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What gears do you have?

My 2000 R/T CC gets 14 in mixed driving, about 1/2 60+ MPH and 1/2 city stop and go.

Over on the Dak R/T forum, that was the best ever of all time!

3.92 rear but in O/D it's 2.7.

Truck weighed 4200 last time I took a load of scrap.


I've often thought of swapping in a 3.55 axle to see if there was a noticeable MPG gain or performance loss.

There's a guy in town that clams to have a '99 R/T CC special ordered with 3.19 gears.
I'd like to know what he's getting.
 
68 Fury four door, 5.2 magnum, 727, obd1 injection, 2.76 gears, it would consistently get 16 to 18 in mixed driving, 21 on a trip. I took the 2.76s out and replaced them with 2.94s and my best is around 20. The 2.76s are now in my dart, because a guy I know told me to :)
 
ocdart said:
I know this is 'apples and oranges' but, just for comparison, my '09 Ram 1500 with a 5.7 Hemi has shown a best of 25mpg freeway cruising at 65mph.
Fairly heavy, aerodynamic-deficient truck rated at 390hp. Can't ask for much better than that.
Click to expand...
Different trans, apparently some of them have tall gears, and MDS- so it's farly different. Even the 4.7 has a different trans which can affect it. By far the majority of trucks I've seen had 3.55s, 3.54s, or 3.92s in them. All the V8 Jeeps had 3.73s back then.

Lelo Dart said:
Same gears. 99 Dakota R/T. Whats a R/T CC? Really doesn't seem to matter how I drive, 14-16 mpg.
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Club cab.

YY1 said:
What gears do you have?

My 2000 R/T CC gets 14 in mixed driving, about 1/2 60+ MPH and 1/2 city stop and go.

Over on the Dak R/T forum, that was the best ever of all time!

3.92 rear but in O/D it's 2.7.

Truck weighed 4200 last time I took a load of scrap.

I've often thought of swapping in a 3.55 axle to see if there was a noticeable MPG gain or performance loss.

There's a guy in town that clams to have a '99 R/T CC special ordered with 3.19 gears.
I'd like to know what he's getting.
Click to expand...
All R/Ts had the same gears. Chances are those "3.19" gears are three-nineties. The tall gear was 3.21, and supposedly some of those trucks/'Rangos got them- apparently Hemi trucks do too. 3.55s were horrendously common after the OD trans was intro'd. Your mixed would be mirroring that best.
 
CC is club or extended cab.

IIRC 3.92 was the standard gear for the R/T.

The guy I'm talking about bought the truck new, and is good friends with a local Mopar head mechanic that I've known for 20+ years and trust implicitly.

Why would he need to special order the stock 3.92 ratio?

My truck will get 23 MPG at 50 MPH, any slower is worse, any faster gets progressively worse.

This is all via the EVIC, which I verified three times. It is actually off by .5 MPG over three entire tanks, but in my favor, IE- EVIC says 13.4, but the math says 13.9, again over three tanks, so IMO it's pretty well "on". I also verified with a "scanguage II" which confirmed my findings.
 
I also had use of my bother's 92 5.2 Dakota CC for about three weeks.

On the same drive routine, that truck got 16 MPG with 3.55 gears and O/D.

Not a lot of difference for a smaller engine and higher gears.

Note that this is the "good" year 5.2 with the larger exhaust manifolds.
 
Just for giggles, I'll throw in my mom's 2002 QC (quad cab) Dakota with a 3.9.

Not sure on the rear gear for that truck, but on the same "test loop" drive routine it got 18.25 MPG. Again, not a crazy difference for such a drastic decrease on engine size and power. Of course, I'm sure that truck is a bit heavier.
 
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